Centralized computer systems with multiple terminal systems for accessing the centralized computer systems were once the dominant computer system architecture. These initially very expensive mainframe or mini-computer systems were shared by multiple computer users wherein each computer user had access to a terminal system coupled to the mainframe computer.
In the late 1970s and early 1980s, semiconductor microprocessors and memory devices allowed the creation of inexpensive personal computer systems. Personal computer systems revolutionized the computing industry by allowing each individual computer user to have access to their own full computer system. Each personal computer user could run their own software applications and did not need to share any of the personal computer's resources with any other computer user.
Although personal computer systems have become the dominant form of computing, there has been a resurgence of the centralized computer system model wherein multiple computer users access a server system using individual computer terminals. Computer terminal systems can have significantly reduced maintenance costs since computer terminal users cannot easily introduce computer viruses into the main computer system or load other unauthorized computer programs. Terminal based computing also allows multiple users to easily share the same set of software applications.
Modern personal computer systems have become increasingly powerful over the decades such that a modern personal computer system is more powerful than the mainframe and mini-computer systems of the 1970's. In fact, modern personal computer systems are so powerful that the vast majority of the computing resources in modern personal computer systems generally sit idle when a typical computer user uses a modern personal computer system. Thus, personal computer systems can now easily serve multiple computer users.